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 Post subject: Re: Runaway.
PostPosted: 26 Apr 2017, 11:21 
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Joined: 12 Jun 2007, 13:36
Posts: 1142
There's nothing on the ATSB or OTSI pages yet. They usually put up a notification pretty quickly. Not that anyone in the industry within 10000km needs to be told, the grape vine being what it is.

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 Post subject: Re: Runaway.
PostPosted: 27 Apr 2017, 12:09 
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Joined: 11 Dec 2011, 11:56
Posts: 152
Atsb reports maximum speed of 118 kmh and no damage to the train. I guess the cab seats just hosed clean.


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 Post subject: Re: Runaway.
PostPosted: 27 Apr 2017, 14:12 
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Joined: 23 Jul 2007, 14:49
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Location: about 1km south of EH23.15
fzr560 wrote:
Atsb reports...no damage to the train. I guess the cab seats just hosed clean.

:o :I'm sniggering creepily: :I'm sniggering creepily:

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 Post subject: Re: Runaway.
PostPosted: 27 Apr 2017, 23:08 
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Joined: 15 Jun 2007, 22:10
Posts: 1381
Location: trying to avoid the pineapple and cactus
While on braking, 2 questions

1. What is the difference between Air and Vacuum systems, and is there a better system?

2. On the long trains (iron ore and even Nullarbor), do they have extra compressor cars to keep pressure at the end of the train correct?

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 Post subject: Re: Runaway.
PostPosted: 28 Apr 2017, 12:56 
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Joined: 11 Jun 2007, 23:01
Posts: 11168
Location: Belmore, NSW
cr001 wrote:
While on braking, 2 questions

1. What is the difference between Air and Vacuum systems, and is there a better system?

2. On the long trains (iron ore and even Nullarbor), do they have extra compressor cars to keep pressure at the end of the train correct?


Until a real railwayman comes along, you'll have to make do with a dodgy reply from a postal worker.

1. Vacuum is simpler, and it allows fine graduation on braking. However, all the parts need to be heavier as, by definition, its braking capacity is one atmosphere, and that means a limited braking capacity overall. Consensus is air is the better system.

2. I think those suckers tend to use distributed power with locomotives plonked here and there along the train, so that's where the air is available locally.

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 Post subject: Re: Runaway.
PostPosted: 28 Apr 2017, 16:28 
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A big benefit with vacuum brakes is their ability to be gradually applied, but also incrementally released if you put a little too much brake on. Normal airbrakes are graduated-apply but direct release. Generally speaking vacuum systems are not only heavier but significantly larger to achieve the same braking capacity, as TLD alluded to the best pressure differential they can achieve is 13.8PSI.

For our trains, we use 2-3 loco's on the head end exclusively, and 236 ore cars made up of 118 married-pairs. The only use of compressor cars is in the yard during the dumping process when the loco's are removed from the train and it is indexed by the positioner arm located adjacent to the car dumper. You'll typically find there is not huge difference in front-rear pressure in an air-braked train, anything over 21kpa/3PSI is unusual during the day, but leakage rates tend to increase, sometimes dramatically, during cold nights due to seals stiffening up, pipework contracting, etc.
When you see bankers attached on the rear here, they are properly coupled, but without the air through the bankers from the train. This is slightly different to the Ardglen bankers where the coupler lifter pin is chained up.

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 Post subject: Re: Runaway.
PostPosted: 28 Apr 2017, 21:27 
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Joined: 15 Jun 2007, 22:10
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Location: trying to avoid the pineapple and cactus
Thanks all for the replies.
Much appreciated

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 Post subject: Re: Runaway.
PostPosted: 29 Apr 2017, 22:22 
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Joined: 28 Jul 2007, 16:32
Posts: 3351
Location: Hay nsw
[quote="KRviator"]I'm not sure they were using it faster than it could be produced, rather, they were using it faster than it could be replenished in the Auxiliary reservoir on each wagon. I'd bet a case of Bundy the MR on the loco was within spec and it was the lack of pressure in the wagon reservoirs that has caused the resulting pinapplage.

For those that don't understand railway airbrakes, I'll run through a quick and dirty explanation - 42101 or BiggEd, please fill in any blanks or correct my mistakes.

In NSW, the Brake Pipe (BP) is charged with air from the loco through the Driver's Brake Valve (or Electronic Air Brake on newer equipment) to 500Kpa, which in turn fills a tank located on each wagon called the Auxiliary Reservoir (again, to 500Kpa on a fully-charged train). To make a brake application, the Driver (or Drover) reduces BP pressure, which moves the Triple Valve located on each wagon to permit air from the Aux Reservoir to fill each wagon's brake cylinder. "Relayed wagons" are a little more complex, but the same basic principle applies.

Where Drover's fall down - and what I think will be found in this instance - is not allowing sufficient time to adequately recharge each wagon Auxiliary Reservoir, which, due to basic physics increases with the length of your train. A simple example of this is if you have made multiple applications and as such have 450Kpa in each of your reservoirs and make a 50Kpa BP application (from the initial 500, remember), means even though you have reduced BP pressure by 50Kpa, the effective difference in pressure is nowhere near 50Kpa, and in some cases may be a negative difference that can trigger an unintended release of the brakes following you applying them. Naturally, on a 1:30 descending grade, this can lead to bad things happening, like soiled underwear and the aforementioned pineapples. It must be remembered that simply reducing BP Pressure alone does not apply the brakes. It is the difference in BP vs Aux Reservoir pressure that determines the resulting Brake Cylinder pressure.

Which is why, most - not all - wagons that are used in NSW have a restrictor fitting installed in the exhaust of the triple valve so that when the driver releases the brakes, even though the Aux Reservoir is now being charged (due to the increase in BP pressure) the Brake cylinder pressure is held applied for 30-45 seconds to allow that little bit of extra pressure into the Aux Reservoirs for another brake application when descending hills like this.

If you have big trains that do not have MR-supplemented brakes (like Bigged and yours truly drive) you have perhaps 2-3 effective applications of the brake before any subsequent applications have you making the papers the following morning following your very own runaway. This in itself is not a serious problem, it simply means you attempt to balance the grade with your first application and regulate speed with dynamic braking from the loco rather than serial braking whereby you apply-release-apply-release-apply-shityourself-which is what probably got these blokes in the ****.


KR nothing i can add to that mate you pretty much nailed it.

A Triple Valve as the name suggests does 3 functions....1 It applies the brakes....2 It Releases the Brakes...3 It recharges the system.
Bwana asked about the old days.
Simple answer
The Freights were much shorter and easier to control with relativly simple TV,s such as the Bulb type 3 1/2 inch TV which was basicly a large lump of cast steel with a very complex yet simple brass slide valve inside it...**** easy to take apart and clean then regrease when servicing one.
Trains were also fitted with a Grade control valve GCV which would allow air to be held in the Brake Cylinder BC for a set period depending on which position was Manualy selected by the Car & Wagon Examiner to keep the brakes lightly applied to the wheels while the system was recharging.....Drivers touched these valves at their peril big fucking no no..... we had to set them and certify that we had them set to the correct holding position using a special Brake Certificate called the GCV book as opposed to your standard Brake book.....only Parkes,Lithgow,Enfield and Port Kembla Examiners were qualified for these workings and you had to recertify every 6 months,Oral,written and followed around a train to be recertified by our C&W Trainers

Later the HR middle managment fuckwits decided that choking to death was the way to cut jobs and maintenance cost....choking to death = Fixed exhaust chokes fitted to the TV exhaust....poor mans GCV and pretty fucking ordinary braking wise.

Also fitted to most vehicles is a Load Compensating Valve/Change over valve/Empty/load valve which were to be set or unset depending on wheter the vehicle was loaded or empty...or even part loaded....this valve Increased braking force when in loaded condition.

Modernish TV,s are Either Westinghouse WF type sealed units,No in service maintenance required but if they fail you just unbolt them and replace them with another... Or the.Davies and Metcalfe Distributor Valves....Shithouse pommy crap that the Railways only brought to **** off Westinghouse over pricing.

Hope this is followable as i had to make it simple and less technical.

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 Post subject: Re: Runaway.
PostPosted: 30 Apr 2017, 06:38 
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From how I follow that, the GCV is the answer to my question - yes, the brakes can be held on, if only temporarily, while the aux reservoir was filled. How did I go?

Next question - did it work in the same way for every brake application for the next 6 months until the next certification, or was this something that could be turned on and off? I'm wondering here how quick stops, like dropping a workmate off at the depot before continuing on your journey (as happened until about the 80's or 90's when I'm guessing the OHS overlords put the kibosh on it) were managed?

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 Post subject: Re: Runaway.
PostPosted: 30 Apr 2017, 11:28 
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Joined: 28 Jul 2007, 16:32
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Location: Hay nsw
Bwana wrote:
From how I follow that, the GCV is the answer to my question - yes, the brakes can be held on, if only temporarily, while the aux reservoir was filled. How did I go?

Next question - did it work in the same way for every brake application for the next 6 months until the next certification, or was this something that could be turned on and off? I'm wondering here how quick stops, like dropping a workmate off at the depot before continuing on your journey (as happened until about the 80's or 90's when I'm guessing the OHS overlords put the kibosh on it) were managed?


Bwana from a rusty memory as i have not done GCV working since 2002 when it was fazed out.....it held the brakes on in the IP/Intermeadiate position for 45 seconds and in HP/holding position it was 90 seconds so yep you grasped it very well.

The recertification was not for the vehicles however it was for us Examiners to make sure we remained competent in all its rules....as in you could only have so many vehicles/tonnage on a train with the airbrakes cut out or GCV defective on them and such = x amount of tonnage out of the whole train tonnage, which if was excessive then the shunters/terminal operators had to knock vehicles off the train to get within the specified limits.
Will try to find my Recertification manual later for any corrections i may need to make but i think i have the basic down for you....i hope.


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